linux-kernel - Re: [PATCH net v1] net: netmem: fix skb_ensure

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Message-ID: <aFAsRzbS1vTyB_uO@mini-arch>
Date: Mon, 16 Jun 2025 07:37:59 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, willemb@...gle.com,
	sdf@...ichev.me, asml.silence@...il.com
Subject: Re: [PATCH net v1] net: netmem: fix skb_ensure_writable with
 unreadable skbs

On 06/15, Mina Almasry wrote:
> skb_ensure_writable should succeed when it's trying to write to the
> header of the unreadable skbs, so it doesn't need an unconditional
> skb_frags_readable check. The preceding pskb_may_pull() call will
> succeed if write_len is within the head and fail if we're trying to
> write to the unreadable payload, so we don't need an additional check.
> 
> Removing this check restores DSCP functionality with unreadable skbs as
> it's called from dscp_tg.

Can you share more info on which use-case (or which call sites) you're
trying to fix?